1. Field of the Invention
The present invention relates to an apparatus for optical module test, and more particularly relates to an improved light box performing better quality during an optical module test process.
2. Description of the Related Art
It is well known that an optical module such as a digital camera, a mobile phone camera, a PC camera always needs tests to know if there is any problem with them. One of these tests is performed by using a light box. As shown in FIG. 1, such a conventional light box is given a reference number 10 while an optical module is given a reference number 16. In such test, the resolution, optoelectronic conversion function (OECF), and grey level gradients of the optical module are the features to be examined.
In regard to the conventional light box 10, it is required that the design complies with the standard established by the International Standard Organization (ISO) and Standard mobile imaging architecture (SMIA) when a variety of test charts 15 are chosen for different demands. For example, we may use a standard ISO 12233 test chart 15a as shown in FIG. 2 for testing the resolution of the optical module 16, while use a standard ISO OECF test chart 15b as shown in FIG. 3 for testing the OECF of the optical module 16.
On the other hand, the light box 10 is provided with a lamp 11 and diffuser 12 on the right side while provided with a lamp 13 and a diffuser 14 on the left side. The diffusers 12 and 14 here are used to uniformly distribute the light beams exiting from the lamps 11 and 13 onto the test chart 15, respectively. At the same time, an optical filter 17 is provided between the optical module 16 and the test chart 15 for simulating an environment of light source of various color temperatures.
However, some problems have been encountered with the above-mentioned light box 10. First, the brightness of the light beam from each lamp could be different from the other one for that the life decay of the lamps do not coincide with each other, and which easily results in the non-uniform distribution of brightness and color temperature. Besides, the uniformity degree of brightness of the diffusers is limited by the distance between the lamps and the test chart. Second, since there is the optical filter between the optical module and the test chart, the test result is always affected by the material feature of the optical filter.
In view of these problems, a new light box for optical module test is disclosed. The disclosed light box is able to provide high degree of uniformity for the brightness distribution on the test chart, and an environment of light source of various color temperatures. Especially, the design of the disclosed light box is so totally different from the conventional one that the above mentioned problems can be avoided.